Adhesively edge-padding a stack of collated carbonless paper

Abstract

Known adhesive compositions for edge-padding a stack of sets of collated sheets of carbonless copy paper have not provided both good fanout and good adhesion within individual sets unless used with carbonless copy paper from the company that supplies the adhesive. This problem is here resolved by using a water-based adhesive composition that differs from those in current use simply by adjusting the amount and type of monohydric and polyhydric alcohol. Best results are attained when the polyhydric alcohol is noncrystalline sorbitol.

We claim: 
     
       1. Method of adhesively edge padding a stack of sets of collated sheets to permit the stack to be fanned apart into individual sets, at least one outer face of each set having a coating that serves as a release agent, said method comprising the steps of (1) applying to an edge of the stack a water-based adhesive composition which comprises by weight: (a) from 7.5 to 20 dry weight % of a water-based latex adhesive polymer,   (b) from 2.5 to 12.5% of a noncrystallizing, low-molecular-weight, water-soluble polyhydric alcohol, and as little as 0.5% when the polyhydric alcohol is noncrystalline sorbitol,   (c) from 12.5 to 27.5% of a low-molecular-weight, water-soluble, monohydric alcohol, and   (d) from 40 to 75% of water, and     (2) allowing the applied adhesive composition to dry.   
     
     
       2. Method as defined in claim 1 wherein said sheets are carbonless copy paper. 
     
     
       3. Method as defined in claim 1 wherein the water-based latex adhesive polymer comprises poly(ethylacrylate/N-methylolacrylamide). 
     
     
       4. Method as defined in claim 1 wherein the water-soluble monohydric alcohol comprises ethyl alcohol. 
     
     
       5. Method as defined in claim 1 wherein the water-soluble monohydric alcohol comprises isopropanol. 
     
     
       6. Method as defined in claim 1 wherein the noncrystallizing polyhydric alcohol comprises 1,2-propanediol. 
     
     
       7. Method as defined in claim 1 wherein the noncrystallizing polyhydric alcohol comprises noncrystalline sorbitol. 
     
     
       8. Method as defined in claim 7 wherein the noncrystallizing polyhydric alcohol is mostly noncrystalline sorbitol. 
     
     
       9. Method as defined in claim 8 wherein the noncrystallizing polyhydric alcohol is entirely noncrystalline sorbitol. 
     
     
       10. Method as defined in claim 1 and further comprising a step (3), fanning the stack into individual sets of the sheets. 
     
     
       11. A stack of sets of collated sheets that have been adhesively edge-padded by the method defined in claim 1. 
     
     
       12. A stack of sets of collated sheets as defined in claim 11 wherein said sheets are carbonless copy paper.